Department of Invertebrate Zoology News - No Bones
This blog contains postings from the broad diversity of individuals who make up the Invertebrate Zoology
community. It is meant to be a spot for reporting both
happenings and topics of interest to IZ community members
to an audience ranging from others interested in
invertebrate zoology to members of the broader
Smithsonian community.

February 2015

26 February 2015

Last week we celebrated Chinese New Year, the festival that marks the start of the New Year according the lunar Chinese calendar. Humans are not the only creatures to time activities by the waxing and waning of the moon’s light. Many species of invertebrates have behaviors that are timed based on the moons rhythms. Here are a few fun examples.

Corals are a diverse group of animals with a wide range of reproductive strategies. Depending on the species, individual corals can be male, female or both. They can reproduce asexually or sexually, and sexual reproduction can take place either internally or externally. Stony corals are mostly broadcast spawners, which is a form of external fertilization. Many of these corals undergo mass spawning events. In a spectacular show coral colonies release huge numbers of eggs and sperm that float toward the surface.

For this type of fertilization to be effective, corals have to closely coordinate their reproductive timing. They do this through the use of three cues, the full moon, sunset, and a pheromone released by other spawning corals. The National Museum of Natural History’s own Nancy Knowlton has been studying coral reefs and their spawning patterns for years, at the Smithsonian Tropical Research Institute's Bocas del Toro field station.

For my money, the palolo worm, has possibly the most fun name to pronounce in the animal kingdom. But these worms are interesting for reasons other than their delightfully rhythmic moniker.

Like corals, these animals use the moon to sync their spawning. Palolo worms, are marine annelid worms of the Eunicidae family that can be found in tropical and temperate oceans worldwide. The species Palola virdis from the south pacific are probably the most well-known as their unusual mating behaviors attract a lot of attention, and were documented in the scientific literature more than 100 years ago! Before breeding, the animal undergoes a partial metamorphosis (epitoky), the back half of the animal transforms and becomes laden with gametes.

When the appropriate part of the lunar cycle arrives, the back section, now called an epitoke, breaks off from the front portion (the atoke) in a process called schizogamy. The epitoke then swims on its own to the surface where it begins to disintegrate, releasing either sperm or eggs. In some places, for instance Samoa and Vanuatu, the aggregations of spawning epitokes are collected and used as a food source. Considered a delicacy, they are prepared in a variety of ways, even eaten raw!

Lunar animal aggregations can have less delicious consequences for humans. Though you may think of jellyfish as animals that are at the mercy of the current, box-jellyfish are actually quite strong swimmers. Box-jellyfish species in the genus Alatina aggregate eight to twelve days after the full moon in parts of Hawaii, Australia, and Bonaire.

Alatina alata in situ images, from Lewis et al. 2013

These aggregations pose a serious threat to beachgoers, often resulting in mass sting events and beach closures. Not just consequences of the current, evidence suggests that these groupings are spawning aggregations. Still curious? We have several previous posts about jellyfish taxonomy, field-collections, research, and outreach. You can even get involved in box-jellyfish research yourself!

As it turns out, many species of marine invertebrates use lunar cycles to synchronize breeding patters, including some species of sea urchins, oysters, various polychaete worms, and crustaceans. But romantic rendezvous under the moonlight are not the only thing invertebrates set their lunar calendars for. Many species of crustacean have been observed to time their molting to certain parts of the lunar and tidal cycle. Crustaceans like all arthropods have a hard exoskeleton; in order to grow they have to molt their old exoskeleton (a process called ecdysis). There are several reasons why syncing molting to lunar/tidal cycles might be advantageous. Firstly, this may allow crustaceans to time their molting to align with favorable tide conditions. Secondly, it is possible that having all the individuals in an area molt at once, decreases individual risk of predation or conspecific aggression -- this is known as the selfish herd hypothesis. The thinking goes that there is safety in numbers; if you are all vulnerable at the same time, predators cannot pick you off one by one. For a specific example take a look at Pseudosquilla ciliata, a mantis shrimp or stomatopod.

Pseudosquilla ciliata (Photo courtesy of the Moorea Biocode Project)

You may remember a bit about these remarkable creatures from our recent post. Research has shown that these mantis shrimp molt during the last lunar phase. Since these animals are highly aggressive towards one and other, molting at the same time reduces the chance of individual mortality. If you molt at the same time as everyone else, you will not be left defenseless, while others are armored and ready for a fight!

So while you usher in the year of the goat, take a moment to think about our invertebrate friends, and the myriad ways that their biology is tied to lunar cycles.

23 February 2015

Have you ever had a vaccine? A shot of morphine? An antibiotic injection? Then you should thank the horseshoe crab for your health. Every FDA-certified parenteral drug (a drug injected into the bloodstream) must meet a battery of standards, one of which is its purity with respect to harmful bacterial endotoxins. For example, the sickness caused by eating undercooked or “bad” meat is due to the endotoxin compounds in the bacteria living on that meat. Even in small concentrations, these compounds can cause disastrous health problems when passing through the digestive tract—which is why you really don’t want bacterial endotoxins in any medications or vaccines that are injected directly into your bloodstream. Thankfully, horseshoe crabs produce a very unique compound that modern medicine uses to ensure that vaccines, antibiotics, and other injected drugs are safe—keeping you healthy.

By nature of its lifestyle, foraging around in sediment in search of small clams, worms, and other crustaceans to eat, the horseshoe crab is constantly exposed to very large concentrations of endotoxin-containing bacteria. A horseshoe crab’s carapace protects the delicate tissues beneath, which include large sinus cavities where the crab’s blood comes into direct contact with its various tissues. Because these invasive bacteria can access the crab’s tissues more directly than in our own bodies, and the crab’s exposure to such harmful bacteria is significantly greater due to foraging, the horseshoe crab has evolved a magnificent defense mechanism, known as Limulus amebocyte lysate (LAL). Horseshoe crabs produce this special compound in their blood, where LAL can quickly coagulate on any endotoxin-containing bacteria that invade the crab’s circulatory system. This coagulation process incapacitates the bacteria, protecting the horseshoe crab.

Mating draws horseshoe crabs to shallow water, where they can be readily captured (and are later released). (Credit: Breese Greg, U.S. Fish and Wildlife Service, Wikipedia)

In 1956, Fred Bang, a researcher at the Marine Biological Laboratories in Woods Hole, Massachusetts, discovered this compound and observed its protective property in the blood of horseshoe crabs. His discovery, spurred by basic natural history observations, led to an unexpected applied result: the LAL test that pharmaceutical companies the world-over now use to ensure that blood-injected drugs are safe for their recipients. To test solutions of drugs for purity, a small amount of LAL is added. If the solution coagulates, the drug contains bacterial contamination. This method is so robust that endotoxin contamination can be detected at extremely low concentrations.

The method calls for the harvesting of large quantities of horseshoe crab blood, which means large numbers of horseshoe crabs are captured annually. It’s a bit of a gruesome process, in which crabs are collected at the shore and then partially bled in a laboratory. On the positive side, this process is more like a blood donation—most of the crabs live and are returned to sea, to continue their bottom-dwelling, sediment-foraging activities.

13 February 2015

Today, the festivities of carnival begin in Rio de Janeiro, Brazil. While Rio may have the biggest party, cities around the world are celebrating with unique and colorful traditions including parades, masquerades, music, dance and costume. We here at No Bones, not wanting to miss out on the revelry, thought we would throw an invertebrate parade of our own. So without further ado let us present the No Bones Carnival Parade: a procession of some festive critters that look ready for a party!

You may remember this amazing animal from our recent post. Not only does the Peacock Mantis Shrimp (Odontodactylus scyllarus) look ready to lead a parade, but their amazing eyesight, powerful appendages and interesting behaviors make these guys quite the character year-round.

While the main body of this animal is safely hidden, the colorful plumes of Christmas tree worms (Spirobranchus giganteus) would fit right in with wild headpieces in a carnival parade. The worm’s multicolored spirals are not just decorative, they are modified prostomial palps that function in feeding and respiration.

Nudibranchs are so diverse and colorful that showing pictures of just a few species cannot really capture the beauty of this amazing group of animals. If you haven’t ever spent an afternoon looking up pictures of these guys, I would recommend it. Here are a few stand out nudibranch specimens from the Moorea Biocode Project.

This clam’s bright mantle not only suits the carnival festivities but also contains symbiotic algae (zoozanthellae).

(Tridacna crocea) (Photo credit: Nick Hobgood, Wikimedia)

Commonly called feather stars or sea lilies, this beautiful animal is a crinoid, a class of animals in the phylum Echinodermata, the same phylum as sea-stars and sea urchins. Its feather-like branching arms give it a festive look that would fit right in on the streets of Rio!

This bubble-tip sea anemone (Entacmaea quadricolor) is rocking mardi gras greens and purples, but these colorful creatures can come in many different color morphs. Bubble-tip sea anemones are one of several anemone species that can maintain a symbiotic relationship with clown-fish.

Arguably the animal kingdom’s master of color, cuttlefish are able to rapidly change their skin color and texture to put on magnificent light shows. Perfect for carnival! Like many of their cephalopod kin they are incredibly intelligent and use their color shifting skills in a variety of complex behaviors.

The oceans are so full of bizarre and beautiful invertebrates that this list could probably go on forever, but we will have to bring this party to a close here. Just remember, during this carnival take a moment to appreciate all the color that life has to offer, whether it is found in a parade or on a polyp!

12 February 2015

On this Darwin Day, it is apropos to note that large sets of observations can lead to transformative ideas. If you have ever read Darwin’s On the Origin of Species, which is an enjoyable experience, you understand.

More than 150 years later, sets of observations have become more enormous than ever and “big data” has become a big buzzword. You’re probably most familiar with big data from the private sector, such as business tracking consumers online, or from the perspective of government and security (think: body worn cameras and Wikileaks). And maybe you’ve read about how big data is revolutionizing healthcare, for example, by supporting electronic medical records and leading to personalized medical interventions based on your DNA.

But what about big data and the department of Invertebrate Zoology (IZ)? You might be surprised to learn that even here in IZ (as well as the Smithsonian more broadly), big data has a big role to play! While “big data” specifically refers to the vast quantities of data that our digital society produces every day, and the associated storage requirements, there are several more important dimensions to big data in the biological sciences. For example, a variety of technological advances in recent years have enabled scientists to collect more data and more types of data faster than ever before, and to ever-greater resolution and accuracy. On the other end, to extract useful information from such vast quantities of data, researchers must have advanced means of data manipulation and analysis.

Researchers deploy ARMS (Autonomous Reef Monitoring Structures) in marine environments to study the local biodiversity. After allowing organisms to adhere to the surfaces of the units, the ARMS are recovered and the organisms are identified through both morphological and genetic studies. (Credit: Barry Brown)

So what does this look like in practice?

IZ’s Sant Chair for Marine Science Nancy Knowlton and postdoctoral fellow Matthieu Leray are both involved in an international collaboration with researchers from Jordan to study the biodiversity in the Gulf of Aqaba. The researchers deploy autonomous reef monitoring systems (ARMS) in the gulf, and then later retrieve the units once marine organisms have colonized their surfaces. Using a process called DNA metabarcoding, the team is classifying the microscopic organisms—many of which are entirely new species. ARMS are also being used in an NSF-funded and SI co-led PIRE project in Indonesian as a platform to train the next generation of biodiversity scientists to address the impact of anthropogenic stressors in marine communities and to understand the assembly of communities in increasingly diverse settings. Lots of organisms means lots of DNA which means lots of data and, of course, lots of scientific discoveries!

Volunteer Mary Mellot put many hours into ensuring that all coral specimens in IZ were catalogued ahead of the collection’s move.

With more than 126 million items in its collection, the National Museum of Natural History boasts the largest and most comprehensive natural history specimen repository in the world. Many of these are historical, and the museum, including IZ, is currently in the process of creating electronic records for all of its specimens, even those dating back to the 1838-42 U.S. Exploring Expedition, the Smithsonian’s first voyage. And every time an IZ researcher heads out on a cruise, new specimens are returned to the museum. In addition to supporting incredibly important biodiversity and conservation research, NMNH’s efforts to develop its electronic and digital offerings are also important for you: open access for the public promotes learning equity, with the potential to bring IZ’s collections directly to schools and individuals in the most remote locations in the United States, and even around the world.

Kids in the San Francisco Bay area do hands-on Biocubing with Chris Meyer.

Many members of IZ are also actively involved in other biodiversity projects that entail large quantities of data management. For example, museum specialist Chad Walter helps maintain the “World of Copepods” section of the World Registry of Marine Species. And research zoologist Chris Meyer has been integral to the development of the Biocube project— which he has promoted in both the research and citizen science arenas. Each instance entails the deployment of a one-cubic-foot frame in a natural environment over the course of a normal day: by identifying the organisms contained within the cube over that time period, the observer creates standardized, comparable records of all species and in the process gains a newfound perspective about biodiversity. As the project has grown, National Geographic photographers, amateur scientists, teachers and students have taken part. More studies, more deployment locations, more observations —that’s a lot of data!

Jamie Baldwin-Fergus, here scubadiving with a large jellyfish, studies the visual adaptations of hyperiid amphipods.

At “the other end” of the data life cycle in IZ. Researchers in IZ rely on many types of data and electronic information for their work, and for the valuable insights they develop using this information. For example, postdoctoral scholar Jamie Baldwin-Fergus combines water quality measurements with computer modeling to reproduce the underwater light environment of hyperiid amphipods recovered from the ocean’s floor. The models help Jamie to better correlate adaptations in eye morphology with the visual abilities of these little-studied creatures.

Clearly, big data is a big deal here in IZ, and plays a central role in not only the research conducted based on the collections but also in making the collections and scientific discoveries accessible to you. But most importantly, technological advances on the front end (better sensors, faster and cheaper DNA sequencing) and the back end (computer modeling software, data management and storage) are what have really shaped the ability of IZ researchers and staff to collect, harness, and utilize so much valuable information about invertebrate species, their communities, and our world.

Aerial view of Mo'orea, French Polynesia, the subject of a big idea based on big data, MooreaIDEA (credit: Wikimedia)

As a final example, consider one of the most ambitious data-driven projects in modern biology: an international team of researchers (including IZ’s Chris Meyer) is building a virtual representation of an entire island! Based on a combination of experimental work, theory—and a mountain of existing data, the Moorea Island Digital Ecosystem Project (MooreaIDEA) will create what is essentially a publically available virtual island. This virtual lab will allow people to generate and test hypotheses about how an ecosystem reacts to various human activities. Big data to support big ideas, indeed.

09 February 2015

While some may give chocolates to the ones they love, there are some individuals that pull out the fireworks and devote a whole light show to attracting potential mates! Meet Photeros annecohenae, a species of ostracod inhabiting shallow seagrass habitat in the western Caribbean Sea. Male P. annecohenae create a beautifully complex bioluminescent courtship display, emitting flashes of blue in the water during the night in hopes of attracting females to mate.

Ostracods are tiny (from less than a millimeter to a few millimeters long), laterally flattened, crustaceans in the family Cypridinidae, which has several species with a neat skill: they possess a special gland (called the light organ) that allows them to create light by secreting compounds [2]. This form of light production is called bioluminescence. Luminescent cypridinid ostracods can use light to for predator defense and/or for courtship displays. Those that use light to surprise and deter predators emit light when threatened or even when swallowed, causing predators to spit them back out in order to avoid being spotted by their own predators [3]. In some species, bioluminescence can also used for mating displays, but only by males. Depending on the species, males employ different patterns of light pulses (seen as a string of dots) that attract only conspecific females, or females of the same species. In the case of P. annecohenae, males show off just how dazzling they can be by performing little dances in which they emit short bursts of light through reactions by luciferin and luciferase, secreted from their upper lip, as they ascend vertically up the water, all in hopes of finding a mate [3].

Just as a fireworks show takes place during the night when the brilliance of light can really wow the audience, P. annecohenae’s courtship display is performed nightly, in absolute darkness, when males have the best chance of being spotted by females. At this time of the night, they initiate their “dance,” which lasts an average of 45 minutes. Their display begins with a stationary phase, in which they produce second-long (or less) pulses of bright blue light, catching the attention of potential female mates. Then, in the next phase, called the helical phase, males spiral vertically up the water column and create more rapid flashes of light that are less bright, traveling about 60 centimeters (2 feet) total [4]. If a male is successful and an interested female approaches, the male grabs onto his newfound partner with his first antennae and the pair sexually reproduce through internal fertilization.

However, because sexual selection is most likely at play here, competition between males is very common [2, 5]. There are three different types of male contenders, all hoping to find a mate: 1) those that are first to begin their luminescent displays, 2) those that entrain, or synchronize, their displays next to the leading males, and finally, 3) those that do not display at all and instead stealthily sneak into another male’s courtship as a female approaches the displaying male and mate with her surreptitiously [4].

This is a series of images showing how a typical nightly courtship display would look like, where certain males initiate the display (2), others follow (3), and different species display their own unique “light shows” nearby (4 and 5). (Courtesy of Gretchen Gerrish [4])

One can imagine how all these courtship displays can in concert form a larger luminescent display against the black backdrop of the nighttime ocean— P. annecohenae sure know how to impress potential mates! Attracting others with a flashy dance seems to have worked rather well for P. annecohenae, so next time you are out on the dance floor, think about adding some glow sticks or standing right where the disco ball hits you just right!

05 February 2015

From the pinks and pastels of Valentine’s Day to the royal purples, greens and golds of Mardi Gras, the celebrations of February certainly do not lack for color. The same can be said of the mantis shrimp. If you are a fan of invertebrates, you most likely are familiar with these awesome crustaceans. They are undoubtedly some of the most charismatic and coolest animals in the ocean.

The term mantis shrimp is the common name for animals of the order Stomatopoda, which contains nearly 500 known species (with many more to discover, see below). Stomatopods can range in color from neutral browns to incredible neon hues that would make them at home in a Carnival parade. But the neatest color story when talking about mantis shrimp isn’t their color, it’s the way that they see color. Human eyes have three types of color photoreceptors (cones cells), each of which specializes in detecting one small range of visible light, or color, for a total of three colors.

These three cone cell types are described as “L” for long wavelengths (which corresponds roughly to red), “M” for medium wavelengths (roughly green), and “S” for short wavelengths (roughly blue). By combing these three cell types, much like the combination of red, green, and blue pixels creates the image on a TV screen, humans can perceive the entire range of color, or visible light, that we experience in our daily lives. Just think of the beautiful color palette in a sunset!

However, the eyes of mantis shrimp far surpass the vision capabilities of humans. Instead of three types of color-sensitive photo receptors, mantis shrimp have 12! Some of these receptors are even sensitive to light in the ultraviolet range, which is outside the visible light spectrum for humans. Even so, mantis shrimp don’t necessarily see color in more detail than humans. New research shows that their ability to discriminate between hues is limited. Unlike human vision where adjacent spectra are compared, in the eye of the mantis shrimp, each of the 12 photoreceptors picks up a specific color and identifies only that color. Overall, this makes the eye of the mantis shrimp less sensitive to color variations than humans, but it also requires less brain processing power. On top of all that, mantis shrimp can see polarized light. These advanced eyes have even inspired the development of new camera technology for detecting cancer.

If these critters’ awesome eyes didn’t already sound as awesome as a super-hero, they pack a punch that would put Superman to shame! Mantis shrimp are fierce hunters and have two raptorial appendages on the front of their body. The morphology of these appendages separates the mantis shrimp into two groups, smashers and spearers.

They use these weapons to hunt in exactly the way their names suggest—by smashing or spearing their prey. In fact, mantis shrimp have the fastest strike in the animal kingdom. Their blows can reach a peak velocity of 23 meters per second (75 feet per second), and can accelerate at speeds of 104 kilometers per second2 (65 miles per second2). The strike takes on average about 2.7 milliseconds. For comparison, blinking your (human) eye takes about 100-400 milliseconds. In that one blink, a mantis shrimp could have smashed or speared its prey 100 times!

These shrimp pack quite a punch as well, striking with 1500 newtons (or about 337 pounds of force). For comparison professional boxers hit with about 5000 newtons.The blows are strong enough to easily break through the shells of prey, and have even been known to crack aquarium glass.

The blistering speed of the shrimp’s strike causes the water in front of the claw to vaporize, creating a cavitation bubble. Cavitation is a phenomenon that happens when liquid is subject to rapid changes in pressure causing the formation of a vapor cavity in the liquid that subsequently implodes, resulting in a violent shockwave. The prey of mantis shrimp are subject to a one-two punch, the blow itself and the shockwave that follows. This shockwave may be enough to stun prey on its own, even if the prey manages to dodge the initial strike. high-speed video of these animals in action. In light of the extreme forces placed on the raptorial appendages of the mantis shrimp, these structures are surprisingly hardy. Their composition has even been studied in order to try and improve combat body armor for soldiers.

But mantis shrimp are lovers as well as fighters. Over a lifetime, one mantis shrimp can have twenty to thirty breeding seasons. Mantis shrimp show a range of complex behaviors related to breeding, including the use of florescent signaling patters and ritualized fighting. Specific mating behaviors, vary by species. Some species are quite promiscuous, while other species are serially monogamous, staying with one partner for a breeding cycle. A hand-full of species have even been reported as being long-term socially monogamous, staying with one partner for longer than one breeding cycle. In fact, the genus Pullosquilla not only shows long-term monogamy but biparental care of the eggs. In other words, both the male and female shrimp parents will assist in looking after the eggs, which is extremely rare in crustaceans. Monogamous mantis shrimp may work together in other ways as well, such as living in the same burrow and sharing hunting duties.

Mantis shrimp are diverse and extraordinary creatures, and we still have a lot to learn about them. A recent study by NMNH collaborator Paul Barber and Sarah Boyce found that Indo-Pacific stomatopod diversity is severely underestimated. One thing is certain they make our oceans a little more colorful!

02 February 2015

Read the science and health sections of any major news website these days and it seems like all we’re hearing about is infectious diseases: ebola, measles, poliovirus, E. coli. As humans, today we have access to vaccines, water purifiers and sanitizers, antibiotics, and many more marvels of modern healthcare to aid us against disease. Undoubtedly, we have reduced human morbidity and mortality related to disease and lengthened our lifespans, but do you ever wonder how wild animals—especially those species often viewed as “primitive” and “less complex” like sponges, jellyfish, anemone, worms, or mollusks—cope with disease?

Many invertebrate groups may seem primitive, but these lineages evolved hundreds of millions of years ago, and the fact that they’re still around in multitudes suggests that whatever their immune systems are, they definitely work!

Invertebrates of all kinds rely on effective immune systems to ward off infection.

An organism’s outermost layer serves as a primary line of defense, because it is a physical barrier against invaders. For vertebrates, it’s the skin. Many invertebrates, like starfish and cephalopods, also have a thick layer of skin, sometimes covered in spines or color-changing skin cells, but always serving to protect the animal. Bivalves have shells made of calcium carbonate, and of course lobsters and crabs have tough exoskeletons made of chitin. Still others secrete mucous, either to protect their delicate skin or to directly ward off predators. Mucus, which is continuously renewed, can trap tiny invaders and then slough them off the body. Moreover, mucus layers are rich in microbial species, which interact in complex processes that appear to play fundamental roles in disease and immunity.

We are still learning about the details and complexities in the evolution of animal immune systems, a tall task considering how enormously varied in their evolutionary histories. Here are a few specific examples:

The comparatively simple (but effective!) immune system of the multi-celled, tiny hydra includes a thin epithelium full of antimicrobial peptides, which help prevent infection.

The jellyfish, composed of about 95% water, is a wonder of nature. In some cases, it has been found that jellyfish have an immune system that presents bacterial-specific responses.

The Invertebrate Zoology department’s octocoral depends in part on photosynthetic algae, and other microbes, for its survival.

By comparison, the defensive mechanisms employed by coral are rather sophisticated (or at least studied in better detail). A coral’s immune system can identify and respond to specific pathogens. Because the coral’s immune system can also identify allografts, coral polyps can fuse into colonies, while other opportunistic infections can be fought off.

Some worms are employed as model organisms because of their simplicity, which is conducive to laboratory studies aiming to understand basic systems in animals. Such studies have revealed that worms possess innate immunity. The signal cascades that initiate the worm’s response to an infectious agent provide the immune system with the ability to recognize different pathogens.

Bivalves, like worms, rely solely on their innate immune response. Phagocytic cells in the blood eliminate infections by attacking invasive organisms with harsh enzymes or reactive oxygen species. And like the hydra, bivalves also possess antibacterial peptides.

Like the other invertebrates mentioned above, the immune systems of crabs cannot develop antibodies to fight infection. Instead, the crab produces compounds that bind to invading bacteria, viruses, and fungi, inactivating these disease-causing agents and even serving as a clotting agent that can help with wound control.

The variety of immune responses in invertebrates may be surprising—it may also have you wondering why starfish on the West Coast have fallen victim to a recent mass die-off. Officially known as “sea star wasting syndrome,” more than 20 species have fallen victim, in many areas eliminating every individual. Recently, scientists identified the likely infectious agent, a densovirus, although questions remain about what environmental factors may have contributed to the severity of the outbreak. Hopefully, you’ve also heard of coral bleaching in response to warming waters. Coral bleaching occurs when the photosynthetic zooxanthellae living within the coral’s tissue die or leave the host, as warming waters create an inhospitable environment. Because of their ecological importance, coral disease is an active area of research.

While coral and starfish are among the more charismatic marine invertebrates, all of the above organisms, it should be noted, depend on specific temperatures and other environmental factors for their immune responses to function normally. As oceans continue to change in response to human activities, what will the future bring?